Passenger rail service returns to the suburbs south of Baltimore today with the opening of the newest spur of Maryland's light rail line.

The three-mile stretch of the 22.5-mile Central Light Rail Line slices its way from Patapsco Avenue over the Patapsco River, through woods and past several northern Anne Arundel County communities.

Sleek light rail trolleys will cut the same winding path as the old Baltimore & Annapolis Railroad, the commuter line affectionately known as the "Bumble & Amble" that carried up to 1.7 million people a year before ending passenger service in 1950. From Patapsco Avenue, the line runs south to four new stations: Baltimore Highlands in Baltimore County and Nursery Road, North Linthicum and Linthicum in Anne Arundel County.

The remainder of the southern spur will open in July, with stops at Ferndale and Dorsey Road in Glen Burnie.

Local lawmakers, commuters, baseball fans, merchants and old-timers who remember the B&A's heyday have awaited a comparatively painless trip to Baltimore, carloads of potential customers and a boost for local home values for more than three years. The state negotiated two years on the price of the six-mile right-of-way, then spent more than a year on construction.

"It's another weapon in the arsenal of surface transportation the state has, a convenient, safe, economical way to get to and from work," said O. James Lighthizer, state transportation secretary.

While light rail's northern spur sparked bitter battles in Baltimore and Baltimore County, he said, "the citizens of Anne Arundel County were by far the most receptive to light rail."

Trains will begin carrying passengers at 6 a.m. today, in time for the Orioles 3:05 p.m. exhibition game against the Pittsburgh Pirates. MTA officials predict a slim turnout until Monday, when hundreds of passengers are expected to ride trains to and from Opening Day at Camden Yards.

Trains will run every 15 minutes from 6 a.m. to 11 p.m. Monday through Friday, from 8 a.m. to 11 p.m. Saturdays and from 11 a.m. to 7 p.m. Sundays. On ballgame nights, trains will run until 11 p.m., or an hour past the end of the game.

Round trips between any two points on the light rail line cost $2.50, or 90 cents for senior citizens. Children under 6 accompanied by an adult ride free.

Rail passengers can park at the 162-space lot at North Linthicum Camp Meade Road near Baltimore Annapolis Boulevard; at Nursery Road, which has 37 spaces; or at Baltimore Highlands, with 50 spaces.

The system opened from Timonium to Camden Yards last

spring, and from Camden to Patapsco Avenue in August.

Some 8,000 passengers ride light rail daily, said Dianna Rosborough, a Mass Transit Administration spokeswoman. But officials project even heavier use on the line from Camden Yards south, based on the number of people now riding buses. The MTA will begin dropping duplicate bus routes and adding feeder buses to rail stops.

"It'll be much more convenient for me to come back and forth to work," said William Marshall, 40, who now walks more than a mile and transfers buses twice to get from West Baltimore to his maintenance job at Lynn Hill Apartments in Linthicum.

Once the Dorsey Road stop opens with 780 parking spaces, the number of people taking light rail anywhere along the line to baseball games should double from last season's average 3,000 per game, Ms. Rosborough said.

"The total travel time from [Dorsey Road] to Camden is 22 minutes -- you won't be able to beat that," she said.

Maryland's central rail line will be the prototype for future state rail systems, officials said. By 2010, light rail's southern spur is expected to generate twice as many passengers as the northern end, with 22,000 daily riders from south of Camden Yards and 11,000 from points north of the ballpark, said Ken Goon, MTA planning director.

Transportation officials plan a 2.5-mile spur to Baltimore-Washington International Airport, possibly by 1996, that would branch out from the main line south of the Linthicum station and cut through airport property. They also plan a 4.5-mile offshoot to Hunt Valley and a half-mile spur to Pennsylvania Station, possibly by 1996.

State officials had hoped to open the southern spur by last year's inaugural Opening Day at Oriole Park. But two years of wrangling over the right of way price delayed the start of construction until August 1991. The state purchased the right of way from Ken Pippin, the owner of the B&A Railroad, a freight hauler for the past 43 years, for $9 million in 1991.